Influence of dietary calcium and phosphorus content in a fixed ratio on growth and development in Great Danes

OBJECTIVE

To study the musculoskeletal development of Great Dane puppies fed various dietary concentrations of calcium (Ca) and phosphorus (P) in fixed ratio by use of dual energy x-ray absorptiometry (DEXA), determination of serum insulin-like growth factor 1 and parathyroid hormone concentrations, radiography, and blood chemistry analysis results.

ANIMALS

32 purebred Great Dane puppies from 4 litters.

PROCEDURE

At weaning, puppies were assigned randomly to 1 of 3 diets. Blood was collected for biochemical analyses and hormone assays, and radiography and DEXA were performed through 18 months of age. Changes in body weight, bone mineral content, fat tissue weight, lean mass, result of serum biochemical analyses, hormonal concentrations, and radius lengths were analyzed through 18 months of age.

RESULTS

Bone mineral content of puppies correlated positively with Ca and P content of the diets fed. Significant differences between groups in bone mineral content, lean mass, and body fat were apparent early. The disparity among groups increased until 6 months of age and then declined until body composition was no longer different at 12 months of age. Accretion rates for skeletal mineral content, fat, and lean tissue differed from each other and by diet group.

CONCLUSIONS AND CLINICAL RELEVANCE

Ca and P concentrations in the diet of young Great Dane puppies are rapidly reflected in the bone mineral content of the puppies until 5 to 6 months of age, after which hormonal regulation adjusts absorption and excretion of these minerals. Appropriate Ca and P concentrations in diets are important in young puppies < 6 months of age.

Effect of cisplatin on bone transport osteogenesis in dogs

OBJECTIVE

To document effects of cisplatin on regenerate bone formation during the distraction and consolidation phases of bone transport osteogenesis.

ANIMALS

10 skeletally mature hounds.

PROCEDURES

Bone transport osteogenesis was performed to reconstruct a 3-cm defect in the radius of each dog. Five dogs were randomly selected to receive cisplatin (70 mg/m2, IV, q 21 d for 4 cycles), and 5 were administered saline (0.9% NaCl) solution. Bone mineral density was measured by use of dual-energy x-ray absorptiometry (DEXA) on days 24, 55, and 90 after surgery. Dogs were euthanatized 90 days after surgery. Histomorphometry was performed on nondecalcified sections of regenerate bone. Bone mineral density and histomorphometric indices of newly formed bone were compared between groups.

RESULTS

Densitometric differences in regenerate bone mineral density were not detected between groups at any time period. Cisplatin-treated dogs had decreased mineralized bone volume, decreased percentage of woven bone volume, decreased percentage of osteoblast-covered bone, increased porosity, and increased percentage of osteoblast-covered surfaces, compared with values for control dogs. Lamellar bone volume and osteoid volume did not differ significantly between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Regenerate bone will form and remodel during administration of cisplatin. Results of histomorphometric analysis suggest that bone formation and resorption may be uncoupled in cisplatin-treated regenerate bone as a result of increased osteoclast activity or delayed secondary bone formation during remodeling. These histomorphometric differences were modest in magnitude and did not result in clinically observable complications or decreased bone mineral density as measured by use of DEXA.

Effects of immobilization followed by remobilization on mineral density, histomorphometric features, and formation of the bones of the metacarpophalangeal joint in horses

OBJECTIVE

To determine microradiographic appearance, bone histomorphometry, and mineral density of the long bones of the metacarpophalangeal joint in horses after immobilization followed by remobilization.

ANIMALS

5 healthy horses.

PROCEDURE

One forelimb of each horse was immobilized in a fiberglass cast for 7 weeks, followed by 8 weeks of increasing exercise. Calcein and oxytetracycline were administered IV during the immobilization and exercise phases, respectively, for bone labeling and analysis after euthanasia. Sagittal sections of metacarpal bones and proximal phalanges were examined via radiography, dual energy x-ray absorptiometry, histomorphometry, and bone label analysis.

RESULTS

Radiography revealed loss of bone mineral opacity in the subarticular regions of the immobilized metacarpal bones and phalanges and subchondral lesions in metacarpal bones in 2 horses. In phalanges, a significant decrease in subarticular volumetric bone mineral density was detected. There was significantly less bone volume and calcein-labeled bone surface and more vascular volume and oxytetracycline-labeled bone surface in immobilized phalanges, compared with contralateral phalanges.

CONCLUSIONS AND CLINICAL RELEVANCE

Eight weeks of exercise after single-limb immobilization is insufficient for recovery of volumetric bone mineral density. During immobilization and remobilization, the subchondral and trabecular bone appear to be actively remodeling.

Clinical evaluation of the effects of immobilization followed by remobilization and exercise on the metacarpophalangeal joint in horses

OBJECTIVES

To evaluate clinical effects of immobilization followed by remobilization and exercise on the metacarpophalangeal joint (MPJ) in horses.

ANIMALS

5 healthy horses.

PROCEDURE

After lameness, radiographic, and force plate examinations to determine musculoskeletal health, 1 forelimb of each horse was immobilized in a fiberglass cast for 7 weeks, followed by cast removal and increasing amounts of exercise, beginning with hand-walking and ending with treadmill exercise. Lameness examination, arthrocentesis of both MPJ, single-emulsion radiographic examination, nuclear scintigraphic examination, ground-reaction force-plate analysis, and computed tomographic examination were done at various times during the study.

RESULTS

All horses were lame in the immobilized MPJ after cast removal; lameness improved slightly with exercise. Force plate analysis revealed a significant difference in peak forces between immobilized and contralateral limbs 2 weeks after cast removal. Range of motion of the immobilized MPJ was significantly decreased, and joint circumference was significantly increased, compared with baseline values, during the exercise period. Osteopenia was subjectively detected in the immobilized limbs. Significant increase in the uptake of radionucleotide within bones of the immobilized MPJ after cast removal and at the end of the study were detected. Loss of mineral opacity, increased vascular channels in the subchondral bone, and thickening within the soft tissues of the immobilized MPJ were detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that 8 weeks of enforced exercise after 7 weeks of joint immobilization did not restore joint function or values for various joint measurements determined prior to immobilization.

Total body and regional measurements of bone mineral content and bone mineral density in pigs by dual energy X-ray absorptiometry

Dual energy X-ray absorptiometry (DXA) was used to make total body and regional measurements of bone mineral content, bone mineral density, and bone area during the growth of pigs from 3 to 138 kg. In all, 1,053 total body scans were performed on 587 live pigs. Regional measurements consisted of the front legs, trunk, and back legs. In addition, bone mineral density readings were recorded for the head, pelvis, spine, and ribs. From about 5 to 75 kg, a greater percentage of the total body bone mineral content (BMC) was located in the trunk region. However, the percentage of BMC in the front and back legs continued to increase linearly whereas the percentage of BMC in the trunk region peaked at about 25 kg and then decreased logarithmically. Allometric analysis revealed that up to about 30 kg the BMC increased more rapidly in the trunk region compared to the front or back leg regions (P > 0.05), but after 30 kg the increase in BMC was more rapid in the leg regions (P < 0.05). Overall, the rate of increase in BMC in the back legs was slightly more than in the front legs (P > 0.05). Positive allometric growth of BMC was observed when compared with the increase in bone area for the same region. By far, the highest measured level of bone mineral density (BMD) was in the head region (P < 0.05), followed in order by the front legs, spine, back legs, pelvis, and ribs. Over the entire range of growth from 3 to 138 kg, the highest relative growth coefficient for the increase in BMD occurred in the pelvic and back leg regions and the lowest was in the ribs (P < 0.05). For pigs < 30 kg, the highest growth coefficient for BMD relative to BW was in the spine (P > 0.05). The growth coefficients for BMD in the back legs and total body increased in pigs > 30 kg and those of the front legs and trunk regions decreased.

Osteopenia and reduced serum alkaline phosphatase activity in grazing lambs naturally infected with gastrointestinal nematodes

The effect of gastrointestinal nematode infections on bone development was investigated in growing sheep on pasture. Forty-five weaned lambs from six groups in a two-factorial design incorporating stocking rate (SR; low, medium and high) and presence or absence of infection on pasture were sampled in the late grazing season. Worm counts were performed at slaughter, and the left metacarpal bones were excised for bone assessment. Faecal egg counts and worm burdens, primarily of Ostertagia circumcincta and Trichostrongylus vitrinus, were considerably higher in the high SR infected group ("I-High") than in comparable animals at low or medium SRs, whereas uninfected groups showed negligible egg excretion. Clinical biochemistry revealed significantly reduced serum concentrations of albumin, calcium and alkaline phosphatase in infected lambs. Nematode infections were associated with significant reductions in bone mineral density (30% at high SR), measured by dual energy X-ray absorptiometry, and in bone size (9%). Histomorphometry indicated thinning of the trabecular structure and reduced bone formation in the infected groups, particularly the I-High group. Bone mineral density, bone tissue volume and structural changes were strongly associated with log-transformed worm counts. The study showed that lambs suffering from moderate to heavy degrees of naturally acquired gastrointestinal nematode infection developed marked osteopenia after weaning, i.eduring the later part of the grazing season.

Use of dual energy x-ray absorptiometry for noninvasive body composition measurements in clinically normal dogs

OBJECTIVE

To determine quantitative values for components of body composition in clinically normal dogs of various breeds by use of dual energy x-ray absorptiometry (DEXA) and validate the precision and accuracy of DEXA technology in dogs.

ANIMALS

103 clinically normal sexually intact adult dogs.

PROCEDURE

In a cross-sectional study, Beagles, Pembroke Welsh Corgis, Golden Retrievers, Great Danes, Pointers, Rottweilers, and nonpurebred dogs received total body DEXA scans. For the validation portion of the study, the results of DEXA scans of 6 dogs were compared with values obtained by chemical analyses of tissues from euthanatized dogs to determine the accuracy of this modality in dogs.

RESULTS

Results (coefficient of variation) of the precision tests ranged from 0.10% for lean tissue to 5.19% for fat tissue, whereas accuracy tests revealed a difference between percentage bone mineral content and ash values. Body composition differed by sex, such as higher lean tissue and bone mineral content in males within some breeds, and among breeds. Regardless of body size or weight, the percentage of body weight that was bone mineral ranged from 3 to 4.0% [corrected].

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this cross-sectional study provide valuable body composition data for clinically normal adult dogs, which may have research and clinical applications.

Metabolic alterations in dogs with osteosarcoma

OBJECTIVE

To evaluate changes in resting energy expenditure (REE) as well as protein and carbohydrate metabolism in dogs with osteosarcoma (OSA).

ANIMALS

15 weight-stable dogs with OSA that did not have other concurrent metabolic or endocrine illness and twelve 1-year-old sexually intact female Beagles (control dogs).

PROCEDURES

Indirect calorimetry was performed on all dogs to determine REE and respiratory quotient (RQ). Stable isotope tracers (15N-glycine, 4.5 mg/kg of body weight, IV; 6,6-deuterium-glucose, 4.5 mg/kg, IV as a bolus, followed by continuous-rate infusion at 1.5 mg/kg/h for 3 hours) were used to determine rate of protein synthesis and glucose flux in all dogs. Dual-energy x-ray absorptiometry (DEXA) scans were performed to determine total body composition.

RESULTS

Accounting for metabolic body size, REE in dogs with OSA was significantly higher before and after surgery, compared with REE of healthy control dogs. The RQ values did not differ significantly between groups. Dogs with OSA also had decreased rates of protein synthesis, increased urinary nitrogen loss, and increased glucose flux during the postoperative period.

CONCLUSIONS AND CLINICAL RELEVANCE

Alterations in energy expenditure, protein synthesis, urinary nitrogen loss, and carbohydrate flux were evident in dogs with OSA, similar to results documented in humans with neoplasia. Changes were documented in REE as well as protein and carbohydrate metabolism in dogs with OSA. These changes were evident even in dogs that did not have clinical signs of cachexia.

Evaluation of dual energy x-ray absorptiometry for in situ measurement of bone mineral density of equine metacarpi

OBJECTIVE

To determine the accuracy and precision of dual energy x-ray absorptiometry (DEXA) for measuring bone mineral density in horses in situ. Sample Population-12 randomly selected forelimbs from 12 horses.

PROCEDURE

Metacarpi were scanned in 2 planes and DEXA measurements obtained for 6 regions of interest (ROI). Each ROI was isolated and bone density measured by Archimedes' principle. Linear regression analysis was used to determine the correlation between the 2 measurements at each ROI. An additional metacarpus was measured 10 times to determine the coefficient of variation for both techniques.

RESULTS

Dual energy x-ray absorptiometry and bone density were significantly associated at multiple ROI. The addition of age, weight, and soft tissue or bone thickness improved these associations. Repeated measurements had a low coefficient of variation.

CONCLUSIONS AND CLINICAL RELEVANCE

Dual energy x-ray absorptiometry can be used to accurately and precisely measure the bone density in the equine metacarpus. Dual energy x-ray absorptiometry appears suitable for serial in vivo measurement of bone density of the equine metacarpus. Dual energy x-ray absorptiometry may be used for studies to evaluate the effects of diet or drugs on bone density or density changes from bone remodeling that develop prior to stress fractures.

Accuracy and precision of dual-energy X-ray absorptiometry for body composition measurements in rhesus monkeys

Accuracy of body composition measurements by dual-energy X-ray absorptiometry (DXA) was compared with direct chemical analysis in 10 adult rhesus monkeys. DXA was highly correlated (r-values > 0.95) with direct analyses of body fat mass (FM), lean mass (LM) and lumbar spine bone mineral content (BMC). DXA measurements of total body BMC were not as strongly correlated (r-value = 0.58) with total carcass ash content. DXA measurements of body FM, LM and lumbar spine BMC were not different from data obtained by direct analyses (P-values > 0.30). In contrast, DXA determinations of total BMC (TBMC) averaged 15%, less than total carcass ash measurements (P = 0.002). In conclusion, this study confirms the accurate measurement of fat and lean tissue mass by DXA in rhesus monkeys. DXA also accurately measured lumbar spine BMC but underestimated total body BMC as compared with carcass ash determinations.

Asymmetric densitometric and mechanical adaptation of the left fifth metacarpal bone in racing greyhounds

The densitometric and mechanical structural properties of the left and right fifth metacarpal bones of 10 racing greyhounds with a fracture of the central tarsal bone and 10 without a fracture were investigated by dual energy x-ray absorptiometry and a servo-hydraulic materials testing machine. In all the greyhounds the bone mineral density of the left fifth metacarpal bone was significantly greater than that of the right (P<0.001), but there was no significant difference between the degree of asymmetry in bone mineral density in the two groups. The ultimate torque and energy-to-failure of the left fifth metacarpal bone of the greyhounds with a fracture of the right central tarsal bone were significantly higher than in the right fifth metacarpal bone and higher than in both the left and right fifth metacarpal bones of the greyhounds with no fracture (P<0.05). The ultimate torque and energy-to-failure were significantly related to bone mineral density (P<0.005), and 22 per cent of the variation in these structural properties could be explained by variations in bone mineral density. Fifth metacarpal remodelling in response to asymmetric cyclic loading is bone-specific, and structural properties are enhanced in the left fifth metacarpal of greyhounds with a fracture of the right central tarsal bone.

Non-invasive assessment of equine bone: an update

This paper summarizes traditional and current methods of non-invasive assessment of bone in the horse. The description and potential clinical utility of two non-invasive technologies with major development in the last decade are presented, namely, (1) serum biochemical markers for bone turnover and (2) quantitative ultrasound. Serum biochemical markers of bone formation valid in horses are osteocalcin, carboxy-terminal peptide of type I procollagen and bone-specific alkaline phosphatase. The cross-linked carboxy-terminal telopeptide of type 1 collagen c-telopeptides of type I collagen and total deoxypyridinoline are the serum markers for bone degradation. These markers respond more rapidly to skeletal changes than other bone assessment techniques, but ideally each horse needs to be compared with itself. Quantitative ultrasound is radiation free and is a well-tolerated technique for measuring bone properties in horses. This device allows bone speed of sound measurements at various sites using the axial transmission mode along the cortex and gives information about stiffness, architecture, porosity and bone mass.A combination of different non-invasive assessment techniques is recommended for the evaluation of bone biphasic modelling-remodelling activity and the mineral phase with its architecture. The potential clinical and research use of these techniques is considered.

Plasma leptin concentrations in cats: reference range, effect of weight gain and relationship with adiposity as measured by dual energy X-ray absorptiometry

The aims of our study were to determine a reference range for plasma leptin in healthy, normal-weight cats and to measure the effect of weight gain on plasma leptin levels. To increase our understanding of the association between leptin and feline obesity, we investigated the relationship between plasma leptin and measures of adiposity in cats. Twenty-six normal-weight cats were used to determine the reference range for feline leptin using a multispecies radioimmunoassay. In the second part of the study, plasma leptin concentrations were determined in 16 cats before and after approximately 10 months of spontaneous weight gain. Dual energy X-ray absorptiometry scans (DEXA) were performed after weight gain. The tolerance interval for plasma leptin concentrations was 0.92-11.9 ng/ml Human Equivalent (HE) with a mean concentration of 6.41+/-2.19 ng/ml HE. In part two of the study, 16 cats gained on average 44.2% bodyweight over 10 months. The percentage of body fat in obese cats ranged from 34.2 to 48.7%. Mean plasma leptin concentrations increased from 7.88+/-4.02 ng/ml HE before weight gain to 24.5+/-12.1 ng/ml HE after weight gain, (P<0.001). Total body fat and body fat per cent were the strongest predictors of plasma leptin in obese cats (r=0.8 and r=0.78, P<0.001, respectively). In conclusion, plasma leptin concentrations increased three-fold in cats as a result of weight gain and were strongly correlated with the amount of adipose tissue present. Despite elevated leptin levels, cats continued to eat and gain weight, suggesting decreased sensitivity to leptin. This investigation into the biology of leptin in cats may aid the overall understanding of the role of leptin and the development of future treatments to help prevent and manage feline obesity.

Dual-energy X-ray absorptiometry measurement of bone-mineral density in the distal aspect of the limbs in racing Greyhounds

OBJECTIVE

To determine those bones in the distal aspect of the limbs of Greyhounds with fatigue fractures that have the greatest left-to-right differences in bone-mineral density (BMD).

SAMPLE POPULATION

Limbs obtained from 20 Greyhounds.

PROCEDURE

Dual-energy x-ray absorptiometry (DXA) of the distal aspect of each limb and isolated bones from 10 dogs with a fracture of the central tarsal bone (CTB) of the right pelvic limb was performed. High-resolution scanning was performed on excised bones, and BMD measurements of CTB also were obtained from limbs of dogs without a CTB fracture.

RESULTS

The BMD of the accessory carpal bone and calcaneus was not significantly different from the BMD of those bones in the contralateral limb. Although BMD of the CTB of the entire right pelvic limb and isolated bones from dogs with a CTB fracture was lower, compared with values for the entire left pelvic limb, values for isolated CTB from dogs without a CTB fracture were not significantly different. Metacarpal or metatarsal and thoracic or pelvic limb significantly affected BMD for measurements of the entire limb and isolated bones. Left-to-right differences in BMD were greatest for metacarpal 5.

CONCLUSIONS AND CLINICAL RELEVANCE

Asymmetric adaptive remodeling of metacarpal 5 can be detected by DXA. The potentially confounding effects of CTB fracture and unknown racing history made it difficult to interpret BMD changes in the CTB of these specimens. Densitometry could be developed as an in vivo assessment for risk of fractures in racing Greyhounds.

Ultrasound therapy for the prevention and correction of contractures and bone mineral loss associated with wing bandaging in the domestic pigeon (Columba livia)

Figure-of-eight wing bandaging is widely used to treat wing injuries, to immobilize wings before and after fracture repair, and during transient wing paralysis. However, prolonged bandaging can lead to bone loss and to contractures and reduced range of joint motion. Studies evaluating the efficacy of therapeutic ultrasound to reverse and prevent bandaging-associated contractures in pigeons (Columba livia) showed a significant increase in elbow and carpal extension after 10 twice weekly ultrasound treatments when started either 4 or 11 days after bandage placement. In addition, after 42 days of wing bandaging, three ultrasound treatments stimulated a faster reversal of carpal wing rotation loss than removal of the bandage over the 10-day treatment period. Finally, bone loss in response to 28 days of bandaging was significant, progressed at 2.8% per week, and was not affected by ultrasound treatment twice weekly during this period. Therefore, therapeutic ultrasound prevented and reversed loss of wing extension associated with figure-of-eight bandaging but did not lessen the disuse osteoporosis created by bandaging in these birds.

Body composition of growing and adult cats as measured by use of dual energy X-ray absorptiometry

BACKGROUND AND PURPOSE

Total body scans were performed on 89 domestic cats of various ages, using dual energy x-ray absorptiometry (DEXA) to determine body composition, including fat, lean, and bone mineral content. Bone mineral density results from scans also are presented.

METHODS

This cross sectional study included data for cats from a closed colony and from privately owned cats. Data were grouped by age and were analyzed by sex and reproductive status to provide information as to the rate of growth of the individual components of body composition.

RESULTS

The results indicate that the rate of accretion of bone mineral, fat, and lean tissue differs throughout maturation and by sex. Regressions are provided to highlight age- and sex-related differences.

CONCLUSIONS

The results of this study emphasize the benefits of examining the growth of each component of body composition when studying the effects of nutrition, disease processes, or therapeutic interventions.

1Alpha-hydroxyvitamin D3 prevents the decrease of bone mineral density in lactating beagles

We assessed the change of bone mineral density (BMD) in lactating beagles with dual energy X-ray absorptiometry (DXA) and the preventive effect of 1alpha-hydroxyvitamin D3 (1alpha(OH)D3) on the BMD. Beagles, two to five years old, were used for detecting the time course change of BMD. Since the coefficient of variation (CV(%)) on detecting lumber vertebral (L2-L4) and tibial BMD by DXA was about 0.5%, DXA was useful to detect the change of BMD in beagles. There was a marked decrease in vertebral BMD during lactational period in the control group. The BMD levels after weaning were found to reverse to the initial level at mating. The same tendency was observed in tibial BMD as vertebral BMD, though the BMD changes were not marked. Beagles were administered at a dose of 0.1 microg/kg of 1alpha(OH)D3 three times in a week, and it was found to suppress the decrease in vertebral BMD during the breast feeding period. Also, the administration of 1alpha(OH)D3 promoted the prevention of decreased BMD during lactation both in vertebrae and tibiae. Significant effects of 1alpha(OH)D3 administration on tibial BMD were not observed. No adverse effects, such as hypercalcemia and hypercalciuria, were observed during the experimental period. Therefore, DXA was useful for detecting the changes of BMD in lactating beagles and the change of BMD was marked in lumber vertebrae, which are rich in trabecular bone. The preventive effect of 1alpha(OH)D3 on the decrease of BMD during the lactation period was observed in beagles.

Effect of age, exercise and growth rate on bone mineral density (BMD) in third carpal bone and distal radius of Dutch Warmblood foals with osteochondrosis

This study aimed a the determining bone mineral density (BMD) in the 3rd carpal bone and distal radius of foals age 5 and 11 months that had been subjected to different exercise regimens from birth until age 5 months. It was hypothesised that BMD would be greater in older animals, and that differences in exercise regimens before age 5 months would be associated with differences in BMD at both age 5 and 11 months. Epiphyseal bone tissue was available from 5 and 11 month old Warmblood foals bred from sires known to have radiographic evidence of osteochondrosis (OC). The foals were in a clinical trial which assessed the effect of exercise up to age 5 months on osteochondrosis (OC). Until age 5 months, foals were either box confined, box confined and sprint trained daily, or kept at pasture. Half the horses in each group were then confined together in a large stall, with access to pasture for 2 h daily, from age 6 to 11 months. BMD was assessed by dual x-ray absorptiometry in 4 areas of interest (AOIs) of excised third carpal bone (C3) and 5 in the distal radius. Volumetric BMD was determined in C3, only surface BMD was analysed in the radius. Across age groups, exercise had an effect on BMD in the mediodorsal and mediopalmar areas of C3. In the 5-month-old animals, the training exercise had similar effect to constant pasture exercise. In all AOIs, BMD was significantly greater in 11-month than in 5-month-old animals. Between age groups there was a difference in effect of exercise regimen before 5 months, in mediodorsal C3 and medial aspect of the radius, and the difference observed between exercise groups at age 5 months was no longer present in horses age 11 months, indicating no residual effect of early exercise. BMD was lower in the group with high OC scores. In the group of horses with the most severe OC, monthly growth rate did not fall uniformly with age over the first 5 months, as it did in groups with lower OC scores. It was concluded that exercise influenced significantly BMD at 5 months, suggesting that carefully designed training programmes to increase bone mineral could be employed in young animals. There was no residual effect at 11 months.

Osteoinductive response in the dorsal aspect of the carpus of young thoroughbreds in training occurs within months

Bone mineral density (BMD) was measured by dual x-ray absorptiometry (DXA) in the carpus of 6 Thoroughbreds age 24 months that were exercised on the treadmill for 4.5 months, and of 6 matched control horses. A sagittal slab of known thickness was sawn from one or more of radius, radial carpal (Cr), third carpal (C3), and third metacarpal (Mc3) bones. After the 4.5 month treadmill exercise, there was a significantly greater volumetric BMD in the dorsal aspect of C3 (P = 0.006). Treadmill-exercised horses also had higher BMD in the dorsodistal aspect of the radius (P = 0.03), the dorsal half of Mc3 (P = 0.012), and the dorsal aspect of Cr (P = 0.04). In other areas of interest (AOI) studied on the palmar aspect of the bones, significant increases in exercised horses did not occur. These sizeable changes in bone mass occurred within a few months of initiation of exercise. With technical development, DXA could be applied in vivo for investigation of changes in bone mass of horses which are growing and exercising under various regimes. The data are also relevant to the development of scientifically based training protocols.

A comparison of dual-energy X-ray absorptiometry and somatometrics for determining body fat in rhesus macaques

OBJECTIVE

Various approaches have been used to assess fat and fat distribution in nonhuman primates, including measurements of body weight, body dimensions, and estimates derived from these, such as body mass index. Methods such as tritiated water dilution and dual-energy X-ray absorptiometry (DXA) have also been used. The aim of the present study was to evaluate and compare DXA measurements and somatometrics.

RESEARCH METHODS AND PROCEDURES

Body composition of 15 adult male rhesus macaques was measured by DXA and somatometrics at four time-points over a 4-year period. Additionally, DXA precision and somatometric variability were analyzed by repeated measurements of the same subjects.

RESULTS

DXA estimates of body fat were positively correlated with body weight, body mass index, body circumferences, and abdominal skinfold thicknesses. DXA assessments of soft tissue composition were precise, with coefficients of variation below 3.3% for all compartments analyzed. The majority of the observed variability in somatometrics was explained by subject variance, rather than by inter- or intraobserver variability, or by observer experience level.

DISCUSSION

We conclude that noninvasive DXA technology provides precise estimates of nonhuman primate body composition that correlate well with the traditional somatometric measures used in primate studies.

Body composition analysis of small pigs by dual-energy x-ray absorptiometry

We evaluated the use of dual-energy x-ray absorptiometry (DXA) for measuring the gross body composition of small subjects in 97 pigs that ranged from 5 to 27 kg live body weight. Scans were performed using a Lunar DPXL densitometer in the pediatric mode (Version 3.8e). The DXA scans of the live pigs provided measurements of total fat, lean, and bone mineral content. After scanning, the pigs were killed, the entire body was ground, and samples were analyzed chemically (CHEM) for fat, protein, ash, and water content. We found that DXA significantly underestimated the percentage of fat in the body (DXA, 6.9+/-.33% vs CHEM, 10.9+/-.31%, P < .001). The correlation (r) between DXA and chemical measures of percentage fat was .86 and for grams of fat it was .96. Lean tissue mass measured by DXA was highly correlated with CHEM measurements of total grams of body water (r = .99), total grams of body protein (r = .94), and lean body mass (r = .99). The average DXA bone mineral content was within 2% of the amount estimated from total body ash and the correlation between the two values was .94. The relationships between DXA and CHEM measurements for percentages of body composition of pigs that weighed between 5 and 27 kg are described by the following regression equations: %fatCHEM = 5.22 + [.817.fatDXA], (r = .86, standard error of the estimate, SEE = 1.56); %proteinCHEM = -7.8 + [.256%leanDXA], (r = .35, SEE = 2.3); %waterCHEM = -5.2 + [.808-%leanDXA], (r = .59, SEE = 3.67). These results are consistent with previously reported results and suggest that even though direct use of DXA readings may not be sufficiently accurate, the high degree of correlation indicates that with proper calibration the DXA values can be used to predict body composition.

Composition analysis of pork carcasses by dual-energy x-ray absorptiometry

Dual-energy x-ray absorptiometry (DXA) was used as a noninvasive method to measure the composition of pig carcasses. A total of 181 half-carcasses (10 to 51 kg, from pigs slaughtered at approximately 30, 60, 90, and 120 kg) were scanned using a Lunar (Madison, WI) DPX-L densitometer. The DXA measurements of fat, lean, bone mineral, and total tissue mass were compared with chemical analysis for fat, water, protein, total ash, and scale weight. The mean value for total tissue mass by DXA was slightly less than the mean carcass weight (32.3 kg vs 33.6 kg, P > .05, R2 = .998). Although highly correlated (R2 = .81), the DXA measurement of the percentage of fat in the half-carcass was less (P < .001) than the chemical measurement (19.5 vs 24.9%). The DXA measurement of lean tissue mass (total mass less fat and bone mineral) was correlated with carcass protein (R2 = .97) and water (R2 = .99) content. The correlation (R2) between DXA bone mineral content and carcass ash content was only .68; however, DXA bone mineral content was more highly correlated with carcass weight (R2 = .93) than was carcass ash content (R2 = .70). When we used the DXA R value (ratio of the attenuation coefficients for fat and lean) to predict percentage of fat in the carcass, the mean value for predicted carcass fat was 25.9% (P > .05). Similarly, carcass protein and water content were predicted from DXA lean. Using DXA region of interest analysis, estimates of the fat content of the shoulder and ham regions were close to chemical values; however, DXA underestimated the fat content of the loin and side regions by 20 and 28%, respectively. When prediction equations were used to evaluate DXA measurements of the half-carcasses of 28 gilts and 37 boars slaughtered at approximately 120 kg, the half-carcasses of gilts contained more fat (33.9 vs 27.8%, P < .001), less protein (14.1 vs 16.1%, P < .001), and less water (45.9 vs 52.1%, P < .001) than those of boars. These results indicate that DXA could be a valuable research tool for measuring the composition of pig carcasses. On the basis of the results of this study, prediction equations were revised for the DXA estimation of fat, protein, and water content of the half-carcass: Fat (%) = 450 - (315 x DXA R value), Protein (g) = -145 + (.23 x DXA lean), and Water (g) = 150 + (.73 x DXA lean). Furthermore, it seems that separate prediction equations are needed for regional analysis.

Deconditioning reduces mineral content of the third metacarpal bone in horses

Diet and exercise are two management factors that affect bone density and strength. We proposed that bone density and calcium status would be affected by deconditioning for 12 wk and by dietary Ca concentration. Eleven highly conditioned Arabian horses were taken out of training and placed in stalls for 12 wk. Horses were walked on a mechanical walker in two 30-min sessions, 7 d/wk. Diets were designated CC (.36% Ca) and HC (.62% Ca). Data were collected every 21 d. Serum or plasma were analyzed for total and ionized Ca, parathyroid hormone, osteocalcin, hydroxyproline, electrolytes, and blood gases. Bone mineral content (BMC) of the left third metacarpal bone was estimated by radiographic photometry using an aluminum step wedge, which was exposed in each radiograph, as a reference standard for an image analysis system. During deconditioning, BMC decreased by approximately 1.1 g/2 cm, or .45% per week. This decrease was unaffected by dietary Ca. Serum Ca concentration increased with deconditioning. The results suggest that dietary Ca at twice the currently recommended level did not prevent the loss of BMC in response to deconditioning. Loss of BMC during 12 wk of stall confinement may weaken bones, increasing the risk of skeletal injuries when training is resumed.

Comparison of dual-energy x-ray absorptiometry and measurement of total body water content by deuterium oxide dilution for estimating body composition in dogs

OBJECTIVE

To compare percentage of body fat (%BF) estimates from dual-energy x-ray absorptiometry (DEXA) with those derived from total body water (TBW) determination by deuterium oxide (D2O) dilution.

ANIMALS

31 healthy, adult, purebred dogs of various ages and breeds (body weight, 15 to 39 kg).

PROCEDURE

The TBW was measured by D2O dilution and subsequent analysis via nuclear magnetic resonance (NMR). Blood was collected before and 2 hours after IV administration of 275 mg of D2O/kg of body weight. Plasma was separated and stored at -30 C until analysis by deuterium NMR. The DEXA scans were obtained immediately after blood collection from dogs under general anesthesia.

RESULTS

Measurements of %BF by DEXA averaged 15.8% higher than calculated estimates of TBW content by D2O dilution. The linear regression of %BF by TBW content on %BF by DEXA had a slope of 1.04 and a correlation coefficient of 0.84, indicating excellent relative agreement between methods despite the significant difference in absolute agreement between the 2 methods. The average difference between methods did not differ by breed, sex, body condition score, body weight, or %BF, as measured by DEXA.

CONCLUSION

Comparability of our data with those of previous studies suggest that DEXA is useful for in vivo estimation of body composition in healthy dogs. Body fat estimated by D2O dilution will be less than that determined by DEXA, despite excellent relative agreement between methods.

Radiographic, densitometric, and biomechanical effects of recombinant canine somatotropin in an unstable ostectomy gap model of bone healing in dogs

OBJECTIVE

To determine the effect of recombinant canine somatotropin (STH) on radiographic, densitometric, and biomechanical aspects of bone healing using an unstable ostectomy gap model.

STUDY DESIGN

After an ostectomy of the midshaft radius, bone healing was evaluated over an 8-week period in control dogs (n = 4) and dogs receiving recombinant canine STH (n = 4).

ANIMALS OR SAMPLE POPULATION

Eight sexually intact female Beagle dogs, 4 to 5 years old.

METHODS

Bone healing was evaluated by qualitative and quantitative evaluation of serial radiographs every 2 weeks. Terminal dual-energy x-ray absorptiometry and three-point bending biomechanical testing were also performed.

RESULTS

Dogs receiving STH had more advanced radiographic healing of ostectomy sites. Bone area, bone mineral content, and bone density were two to five times greater at the ostectomy sites of treated dogs. Ultimate load at failure and stiffness were three and five times greater in dogs receiving STH.

CONCLUSIONS

Using the ostectomy gap model, recombinant canine STH enhanced the radiographic, densitometric, and biomechanical aspects of bone healing in dogs.

CLINICAL RELEVANCE

Dogs at risk for delayed healing of fractures may benefit from treatment with recombinant canine STH.

Biomechanical comparison of the Herbert and AO cortical bone screws for compression of an equine third carpal bone dorsal plane slab osteotomy

OBJECTIVE

To assess feasibility of insertion of 4.5-mm Herbert cannulated bone screws (HS) using fluoroscopic guidance and compare the mechanical shear strength of these HS and 4.5-mm AO cortical bone screws (AO) for fixation of dorsal plane slab osteotomies in equine cadaver third carpal bones (C3).

ANIMALS OR SAMPLE POPULATION

Eight equine cadavers.

METHODS

Bone mineral composition and density of contralateral C3 were confirmed to be equivalent using dual-energy x-ray absorptiometry. A standard 10-mm C3 slab osteotomy was reduced using HS or AO instrumentation under fluoroscopic guidance. Specimens were loaded in shear until failure, using a materials testing apparatus.

RESULTS

HS and AO instrumentation allowed accurate reconstruction of the osteotomy, but there was difficulty encountered seating the HS proximal self-tapping threads. There was no significant difference in maximal load to failure, stiffness, or mode of failure of constructs created with the HS and AO screws.

CONCLUSIONS

Use of 4.5-mm HS for repair of C3 radial facet, dorsal plane slab fractures may result in a mechanically comparable fixation to a repair using a 4.5-mm AO. Equine dorsal C3 may be too dense, however, to allow placement of the proximal self tapping threads of the HS without potentially excessive application of torque to the screw itself.

CLINICAL RELEVANCE

Dorsal plane, radial facet slab fractures of the equine C3 are a significant clinical problem. Accurate reconstruction and stabilization are necessary for return to athletic function.

Body composition analysis of chickens by dual energy x-ray absorptiometry

Dual-energy x-ray absorptiometry (DXA) was evaluated as a method for measuring the body composition of growing broiler chickens. A total of 130 chickens, ranging in weight from 400 to 3,290 g, were scanned using a DXA instrument (Lunar DPX-L). Single whole-body scans were acquired and analyzed using pediatric total body research software (neonatal mode) or small animal total body research software (detail or high resolution mode). The DXA measurements provided readings of total tissue mass, percentage fat, fat tissue mass, lean tissue mass, and bone mineral content. After scanning, the bodies of the chickens were frozen, then, after removing the feathers, homogenized for chemical determination of fat, water, and protein content. By chemical analysis, the whole body fat content of the chickens ranged from 2.8 to 27.2%, giving rise to DXA R values (ratio of attenuation coefficients) ranging from 1.415 to 1.339. The accuracy of DXA for measuring total body fat was a function of the scanning program and mode and also the size of the bird. The best agreement between DXA and chemical measurements of percentage body fat were obtained when chickens weighing more than 2,000 g were scanned using either the small animal-detail mode or neonatal mode. None of the scan modes proved to be accurate for measuring the fat content of birds weighing less than 2,000 g. The DXA measurement of lean mass of chickens was found to be highly correlated with both total body protein (R2 = 0.90) and total body water (R2 = 0.93), but was of little value for predicting percentage values for either. The ratio of DXA bone mineral content to total body ash was 0.77; however, the correlation (R2) between the two was only 0.46. These results suggest that although the DXA technique is potentially useful for measuring body composition of chickens, considerable refinement is needed prior to routine application.

Body composition analysis of pigs by dual-energy x-ray absorptiometry

Dual-energy x-ray absorptiometry (DXA) was evaluated as a method for measuring body composition of pigs. Forty-eight female pigs (10.2 to 60.5 kg) were killed and the whole bodies scanned on a DXA instrument. The DXA measurements provided readings of total tissue mass, percentage of fat, fat tissue mass, lean body mass, and bone mineral content. By chemical analysis, the whole body fat content of the pigs ranged from 9.3 to 24.3%, giving rise to DXA RST values (ratio of attenuation coefficients) ranging from 1.386 to 1.334. The average percentage body fat measured by DXA (18.2 +/- .9%) was not significantly different (P = .76) from the results by chemical analysis (17.8 +/- .6%); however, concordance correlation analysis revealed unacceptable accuracy in the DXA measurement due to a negative bias for smaller percentages and a positive bias for larger percentages. Total body fat measured by the two methods was also highly correlated (r = .989), and the average for DXA (7.31 +/- .62 kg) was not significantly different (P = .89) from the value for the chemical method (7.20 +/- .50 kg). The relationship between the DXA estimate of lean body mass and the amount of protein in the body by chemical analysis was described by the equation: kg protein = .227.kg DXA lean -1.28, with a correlation coefficient (r) of .968. The DXA measurements of total tissue mass and actual body weights were highly correlated (r = .999), with an acceptable concordance at the .05 level. Scans were also analyzed for regional composition of the front and back legs. It was generally difficult to determine anatomically how well soft tissue described by DXA regions corresponded to those dissected. The DXA and chemical results for regional analysis of back legs were in better agreement than those for the front legs. These results indicate that DXA may be used as a reliable method for measuring body composition of pigs, but needs more extensive calibration and may be more appropriate for total body rather than regional analysis.

Changes in the body composition of cats during weight reduction by controlled dietary energy restriction

Thirteen overweight domestic short-haired cats were fed a commercial low calorie diet for 18 weeks at an energy intake to lose weight; they lost an average of 18.1 per cent of their starting weight. An evaluation of their body composition by dual energy x-ray absorptiometry before and after the study suggested that most of the weight lost was composed of fat. The cats' lean bodyweight did not change significantly, but increased as a proportion of total bodyweight.

Dual-energy x-ray absorptiometry and force-plate analysis of gait in dogs with healed femora after leg-lengthening plate fixation

Dual-energy x-ray absorptiometry was used to measure bone mineral density of four regions in healed femora of nine dogs after fracture fixation with a leg-lengthening plate. Six to 85 months (mean, 46 months) after surgery, the bone mineral density of healed femora was not significantly different from the contralateral uninjured femora (P > .05; power = 0.8 at delta = 15%). Radiolucencies around the proximal screws, apparently associated with screw loosening, were seen on radiographic views of the healed femora of three dogs. In one of these dogs, one screw in the proximal metaphysis had broken. Force-plate analysis of gait was also performed on dogs at the time of bone mineral density measurement. Peak vertical force was decreased in the pelvic limb with the healed fracture compared with the contralateral unoperated limb (P < 0.05). Clinically apparent lameness in three dogs did not appear to be associated with altered bone mineral density and may have been caused by hip osteoarthritis, a nondisplaced hairline diaphyseal fracture, and screw loosening in conjunction with extensive post-traumatic soft tissue injury.

Densitometric properties of long bones in dogs, as determined by use of dual-energy x-ray absorptiometry

We performed dual-energy x-ray absorptiometry (craniocaudal and lateromedial views) on 10 pairs of humeruses, radiuses, femurs, and tibias from dogs, using an alignment jig, to determine the homotypic bone mineral density variations of long bones. The bones were divided into 3 regions: proximal, middle, and distal parts of the diaphysis. The bone mineral density of cortical bone, medullary bone, and total bone was determined. Of 160 homotypic comparisons, 21 indicated significant (P < or = 0.05) differences between right and left bones at either a region or location. These differences were observed most frequently in the craniocaudal view and were probably secondary to positioning errors. Evaluation of elliptical bones, such as the radius, also indicated that, when the thicker dimension, such as the lateromedial view of the radius was measured, the bone mineral density of regions-of-interest in that view was greater than that in the opposite view (ie, craniocaudal view of the radius). This study validates the concept of using the contralateral limb as the control condition in orthopedic studies of dogs, particularly when evaluating the densitometric properties of long bones. This study also emphasizes the importance of accurate positioning to prevent inadvertent alteration of bone mineral density results when using dual-energy x-ray absorptiometry. Dual-energy x-ray absorptiometry is particularly susceptible to positioning errors, because it converts a 3-dimensional structure into a 2-dimensional image.

Dual-energy X-ray absorptiometry of canine femurs with and without fracture fixation devices

The effect of 5 fracture fixation methods on bone mineral density (BMD) measurement of femurs, using dual-energy X-ray absorptiometry (DXA) was determined in a canine model. Six regions of interest were measured, including the entire femur, the diaphysis of the femur, and small regions centered over the middiaphysis of the bone (lateral middiaphyseal cortex, medial middiaphyseal cortex, middiaphyseal medullary canal, and total middiaphysis). Eight unpaired femurs were collected and scanned by use of DXA before (5 separate scans/femur) and after (5 separate scans/femur) fixation by use of 1 of 5 fixation methods. These fixation methods included: intramedullary (IM) nail; IM nail and cerclage wires; IM nail and external skeletal fixation; locked IM nail; and a dynamic compression plate (DCP). All implants were made of stainless steel. The IM nail fixation devices caused significant decreases in the DXA measurement of BMD in the small regions of interest, compared with femurs without fixation devices (mean decrease, 37.3%; P < 0.05). The locked nail caused similar, but larger, decreases in the DXA measurement of BMD, compared with the IM nail fixation methods (P < 0.05). Plate fixation caused a small, but significant (P < 0.05), decrease (2.8%) in the DXA measurement of BMD in the large regions of interest, but when all regions were averaged, it did not cause significant change in this measurement, compared with femurs without fixation devices.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of body composition in cats and dogs

The assessment of body composition in any species is important to the understanding of subjects such as the control of obesity, the realimentation of sick animals and the evaluation of energy requirements. In most cases our requirement is to assess the chemical constituents of the body by the measurement of the fat and fat-free mass (FFM) of the subject. There may also be a requirement to break down the FFM mass into its component parts and measure the tissue distribution within the body. Clearly in the understanding of the causes and effects of obesity in companion animals, the evaluation of the actual level of obesity is fundamental. Similarly, whilst classifying the effectiveness of a weight loss programme it is vital that the reduction in weight loss and the distribution of tissue types can be accurately recorded by the veterinary surgeon or clinician. This review covers the theory of body composition measurement and the techniques which have been developed, together with their relevance to studies with companion animals. Most techniques are based on indirect methods which use the model of the body being at least two chemically distinct compartments, the fat and the FFM. In more complex analyses four and even six compartment models are considered which include concepts such as protein content, cell and osseous mineral content. The techniques to be covered include the measurement of total body water (for example by the use of isotope dilution), anthropometric techniques (skinfold thickness and dimensional evaluation), densitometry, total body potassium, muscle metabolite markers, absorptiometry, neutron activation analysis, electrical conductance, ultrasound, near infrared interactance, computed tomography and magnetic resonance imaging.(ABSTRACT TRUNCATED AT 250 WORDS)

[Measuring bone mineral content and soft tissue mass in living the cynomolgus monkey]

Bone mineral content and soft tissue (lean and fat) mass in living female cynomolgus monkeys were successfully measured with a dual-energy X-ray absorptiometry (DEXA; DPX-alpha, LUNARE, USA). Measurements were performed using a restraining bed made of forming polystyrol with 5cm thickness to support the animal in a supine position. Accuracy of measurements was checked by using a dummy consisted by various combinations of lean, lard and ribs. The results confirmed that this system is able to measure each constituent exactly. The percentage of fat in the soft tissue is seemed to be better index of obesity in this primate species when compared with other obesity markers such as body weight and morphometry.

[Age-related changes in bone mineral density, mean width and area of the lumbar vertebrae in male African green monkeys (Cercopithecus aethiops)]

We were able to measure bone mineral density (BMD), mean bone width and the area of the lumbar vertebrae in male African green monkeys with a dual-energy X-ray absorptiometry (DPX-alpha, Lunar, USA). For analysis of spinal bone mass, mean width and area of the bone, we scanned lumbar vertebrae L3-L5 using a pediatric analysis program. We used restraining bed made of formed polystyrol to support the animal in a supine position. The precision of the measuring technique was calculated by averaging the coefficients of variance of the 5 scans obtained in 5 animals aged from 5 to 7 years. The precision values for BMD, bone width and area were 1.9%, 0.9% and 2.6%, respectively. Furthermore, age-related changes in bone measurements were demonstrated using laboratory-bred males (n = 45) and, additionally, wild-originated males (n = 7, estimated ages over 15 years old). The values of B M D, bone width and area at 6 months old were about 0.3 g/cm2, 1.2cm and 4.5 cm2 respectively. These values increased with aging to about 0.7 g/cm2, 1.5 cm and 11cm2 at 5 years old, respectively, and were judged to reach plateau. However, animals over 10 years old and wild-originated animals which had been kept over 10 years in our breeding colony showed rather smaller BMD and area values than the animals aged 5 to 10 years. The animals aged between 5 and 10 years seemed to have retained a peak bone mass in this primate species.

The effect of long-term bone plate application for fixation of radial fractures in dogs

This study was divided into two phases. In the in vitro phase, a stainless steel bone plate was applied to the cranial surface of the radius in 14 canine limbs. The effect of the presence of a bone plate on bone density analysis using radiographic photodensitometry (RP) was evaluated by comparing the density measurement of the unplated limb to the density measurement of the plated limb. The optical density of the plated bones was 12% greater than that of the unplated bones. This information was used as a correction factor for the in vivo study. In the in vivo phase, 23 dogs with radial and ulnar fractures were examined for complications associated with the long-term application of a stainless steel plate applied to the cranial surface of the radius. In 14 dogs, RP analysis was used to compare the plated limb with the normal, contralateral limb. No significant differences in radial cortical bone density existed between the plated limb and the contralateral limb after taking into account the effect a bone plate had on photodensitometry readings. There was no significant correlation between the change in radial cortical density and the duration of bone plate application, suggesting that a steady state between bone loss and bone production occurs after long-term plate fixation of the fractured canine radius. The majority (87%) of the dogs with a plate applied to the radius greater than 1 year had normal limb usage when standing, walking, or running.

Equine cricoid cartilage densitometry

The density of the cricoid cartilage from 29 equine larynges collected from an abattoir was determined by dual photon absorptiometry (DPA). Densities of the right and left cricoid cartilages were highly correlated. No correlation was found between age of the horse and the density of the cricoid cartilage.

Research note: current methods used in determination and evaluation of tibia strength: a correlation study involving birds fed various levels of cholecalciferol

Tibiae were removed from 300 75-wk-old laying hens for tibia strength analysis using two methods, direct photon absorptiometry and tibia breaking strength. Left tibiae with flesh intact were used for bone density determination with direct photon absorptiometry. Right tibiae were cleaned and dried for determination of tibia weight and tibia breaking strength. Partial correlation coefficients were estimated among bone density, tibia breaking strength, tibia weight, and body weight. A significant correlation was observed between tibia breaking strength and bone density measurements (r = .66, P less than or equal to .0001). Tibia weight and tibia breaking strength were also significantly correlated (r = .62, P less than or equal to .0001), as well as bone weight and bone density (r = .71, P less than or equal to .0001). Tibia weight and BW were also significantly correlated (r = .66, P less than or equal to .0001), necessitating covariance adjustment for BW. Bone densitometry measurements are less variable than tibia breaking strength measurements, and bone densitometry does not require cleaning bones of flesh before measurement.

Osteopenic effects of forelimb immobilisation in horses

Methods for the non-invasive assessment of bone quality were used to monitor the osteopenia induced by immobilising a forelimb in a cast. These techniques included the measurement of ultrasound velocity, single photon absorptiometry and radiographic photodensitometry. Serial measurements were made before, during and after an eight week period of immobilisation of the left forelimb of four adult standardbreds in a light fibreglass cast which included the foot and extended above the carpus. The measurements continued for 12 weeks after the removal of the cast. The results indicated a trend to decreasing bone strength and mineral content in both forelimbs, with the decreases being greater in the limb with the cast. The values tended to recover slowly after the removal of the cast, then more quickly after the horses returned to the paddock four weeks later. The differences between the limb with the cast and the opposite limb were significant at only a few points of comparison.

Accuracy and reproducibility of lumbar bone mineral status determined by dual photon absorptiometry in live male cynomolgus macaques (Macaca fascicularis)

Dual photon absorptiometry (DPA) was used to determine the in vivo bone mineral content (BMC) and bone mineral density of lumbar vertebrae (L2-4) in feral adult male cynomolgus macaques (Macaca fascicularis, n = 20). Following in vivo DPA scans, all animals were euthanized and the lumbar spine segment excised. The excised lumbar vertebrae, plus spinal cord, were formalin-fixed and measured three times by ex vivo DPA. The first ex vivo scan matched the monkey's own in vivo soft tissue beam attenuation ratio (Rs, ranging from 1.38 to 1.45). The second ex vivo scan was made creating a constant obese-like condition (Rs = 1.38), and the third creating a constant lean-like condition (Rs = 1.45). All scans were taken at a 1.0 mm point resolution, 1.0 mm line spacing, a 6 cm width, and a scan speed of 5 mm/sec. The second lumbar vertebra (L2) was ashed and the ash weight was compared to the measured L2BMC of the in vivo and ex vivo DPA analyses. Noninvasive in vivo DPA proved to be adequate in measuring the lumbar bone mineral content in male cynomolgus macaques. Ex vivo DPA at a high and constant Rs value of 1.45 provided for the best accuracy of formalin-fixed wet bone tissue when compared to the bone ash weight.

Ultrasonic transmission velocity and single photon absorptiometric measurement of metacarpal bone strength: an in vitro study in the horse

Ten pairs of third metacarpal bones from Thoroughbred horses aged two to 12 years were used to estimate bone strength. Measurements of transverse cortical ultrasound velocity, cortical cross sectional area and bone mineral content were made using ultrasonic transmission velocity and single photon absorptiometry. These data were used to determine bone mineral density, compact bone density and modulus of elasticity. The results were compared with those measured by direct means or chemical analysis and satisfactory correlations were obtained between estimated and measured values. Single photon absorptiometry was found to be more accurate than dual photon absorptiometry. The estimated modulus of elasticity in the transverse direction correlated well with the measured longitudinal value obtained by compression testing. This investigation confirmed the value and precision of using a combined ultrasonic and photon absorptiometric technique for non-invasive measurement of bone strength.

The hock as a potential site for non-invasive bone measurement

An in vitro study on the calcaneus of adult horses (n = 5) and foals (n = 10) was carried out using radiographic photodensitometry, single photon absorptiometry, transmission ultrasound velocity and chemical analysis. Data for trabecular bone content, ash, calcium and phosphorus levels were obtained. As techniques for assessing bone quality, ultrasound velocity was not sufficiently sensitive nor accurate and radiographic photodensitometry was found to be limited value. Photon absorptiometry was both accurate and reproducible, although some variation in bone mineral content and bone mineral density was observed along the length of the calcaneus. Bone mineral content was estimated in a second series of fibular tarsal bones from 23 horses ranging in age from less than six months to 16 years. The photon absorptiometry technique was also applied to the hocks of four hind limbs at post mortem and two horses under general anaesthesia. It was concluded that the calcaneus was a feasible site for photon absorptiometry, but that the present equipment would require considerable modification for use in the standing horse.

Monitoring the effects of treadmill exercise on bone by non-invasive means during a progressive fitness programme

Six Standardbred horses underwent a 14-week training programme on a treadmill. The training schedule consisted of five weeks of slow work of six to 12 km/day at 5 m/sec. This was followed by a nine week interval programme increasing in its intensity so that for the last three weeks the horses did three to four intervals/day from 600 to 1000 m at or above maximum heart rate. Ultrasound velocity through the third metacarpus showed a significant increase as a result of training. There was also a significant increase in modulus of elasticity, but no change in bone mineral content, bone mineral density or compact bone density. A decrease in ultrasound velocity was noted immediately after a session of trotting on the treadmill for 6 km. These changes reflected the potential to alter the viscoelastic properties of cortical bone through treadmill exercise, but did not explain the mechanism involved.

Non-invasive measurement of bone: a review of clinical and research applications in the horse

The current methods for non-invasive measurement of bone quality are reviewed. In the horse this has traditionally involved the use of radiography, but there are now two other modalities available for the critical evaluation of cortical bone quality and strength. These utilise single photon absorptiometry and ultrasound velocity. Photon absorptiometry gives a direct measurement of bone mineral content, by using a monoenergetic radionuclide source, and transverse ultrasound velocity in bone gives a measure of bone stiffness or elasticity. They can both be used conveniently on the metacarpus of the conscious horse. Both ultrasound velocity and bone mineral content can be used as accurate indicators of skeletal maturity. In addition, the effects of disuse on bone and certain types of lameness can be monitored accurately. Preliminary data show an association with exercise in young and mature horses. There also appears to be considerable scope for in vivo research of bone changes in horses produced by immobilisation, weightlessness, exercise and nutrition.